Spark gap generator



INVENTOR PIERRE MARIE 2 SHEETS-SHEET l GABRIEL TOULON ATTORNEY Y P M G TOULON SPARK GAP GENERATOR Dec. 16, 1952 Filed Aug. 4, 194'? P. M. G. TOULON SPARK GAP GENERATOR 1 Filed Aug! 4, 1947 2 SHEETS-SHEET 2 INVENTOR PiERRE MARIE 'C-ABRIEL TOULON ATTORNEY Patented Dec. 16, 1952 SPARK GAP GENERATOR Pierre Marie Gabriel Toulon, Paris, France, as-

signor to Products & Licensing Corporation, New York, N. Y., a corporation of Delaware Application August 4, 1947, Serial No. 766,035

I In France March 22, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires March 22, 1963 Claims.

My invention relates to a new system for pcriodically generating current impulses by means of a spark gap relay, comprising at least two main electrodes between which a spark discharge is periodically started by the electrostatical triggering action of a third electrode, called the starting or trigger electrode receiving the starting voltage. A high voltage is applied to the main electrodes which insures the breakdown effect, and current impulses of substantial amplitude so produced are fed into a load device in series with these main electrodes circuit. The relay is preferably of an open air type, needing no tight envelope and the starting electrode operates only by an electrostatical effect, changing, according to the potential applied to it, the distribution of the lines of the electric field in the vicinity of the main electrodes. At a certain time, this distribution starts a breakdown of the air gap between the main electrodes, and trigers a current pulse in their load circuit. This system offers the special advantages that no heating current is needed to energize the relay, and that an appreciable amount of energy is triggered, the current impulses being of a substantial amplitude, with a very low and practically negligible loss of power in the starting circuit, with the result that this system is particularly designed to insure a definite relay action from supplies of a, minimum energy. On the other hand, the use of an open air relay makes this system relatively inexpensive to manufacture and maintain and the relay itself is of good mechanical resistance and choke proof According to one feature of the invention, the

main electrodes receive a breakdown Voltage in a form of 'high tension impulses of short duration succeeding in the time by an interval that must not be lower than the deionisation period of the relay. The amplitude of these impulses is so adjusted that, in the absence of the starting electrode action, they do not break down the gap. A continuous, variable amplitude potential is applied to the trigger electrode by the input or triggering circuit. As soon as the amplitude reaches the starting level, the relay breaks down and spark appears at each high tension impulse, transforming therefore a continuous potential of the input circuit into a succession of current impulses of a substantial amplitude.

The breakdown voltage impulses may be realized by a train of high frequency quenched or damped oscillations succeeding in time by a given rate determined by the construction of the relay.

This train of oscillations may be generated in a conventional manner by a discharge of a condenser through an auxiliary gap.

According to another feature of my invention, in order to increase the efficiency of the relay action, an auxiliary source of supply is introduced in series with the main electrodes circuit, discharging through the spark during the breakdown period. This source may be preferably formed by a relaxator comprising a condenser charged through a definite resistance and inserted in the discharge circuit of the relay.

The invention also has for its object an im proved form of air gap relay comprising two main electrodes spaced apart appreciably beyond their normal spark-over distance, and of a spherical form, and, at least, one starting electrode of the annular form fixed near one of these main electrodes and surrounding it. The starting continuous potential is then applied between the two last electrodes.

The novel features which are considered to be characteristic of my invention are set forth in the appended claims. My invention itself, however, both as to its construction and method of operation may be best understood by reference to the following detailed specification taken in conjunction with the accompanying drawing wherein:

Figure 1 is a diagrammatic representation of my pulse generating system comprising an open air gap relay with means to energize the main or load circuit, and means to start the discharge;

Fig. 2 is a diagrammatical representation of my pulse generating system of improved form designed to feed several relays with a single high frequency generator, this system being used to control in their load circuit two are relays of so-called pilot type; and

Fig. 3 represents diagrammatically an application of my system to control an alarm device in response to a slightest potential variation in the primary control circuit.

Referring now to the drawing, I have illus trated at Fig. 1, by reference letter E, an open air spark relay device comprising two main electrodes 4 and 5, and, a triggering or starting electrode 6, in the form of a ring disposed adjacent to electrode 5, these last two electrodes bein practically in the same plane. It must be noted that it is an open air device, therefore with no air-tight envelope. The illustrated system comprises an input or starting circuit connected between this starting electrode 6 and a common ground point. There is inserted in series with this circuit a control device I, the potential of which is app-lied to the starter so as to define its electrostatic action. This device I may be any source of unidirectional potential, which amplitude is variable with the time and is represented as a, direct voltage battery l8 connected to the starter 6 by means of a potentiometer 25 through a sliding contact I.

The illustrated system comprises also an output or discharge circuit in series with the main electrodes of the relay. It is formed by a secondary winding 12 of a high tension high frequency quenched oscillation generator as GT designed as a timing or energizing generator, by a condenser l5 of an energy supply auxiliary generator as GA called after supply generator; and finally by a load circuit U schematically illustrated as an electric lamp M in series with a choke coil I3.

The timing device GT is a well-known quenched H, F. oscillation generator comprising a storage condenser 8 charged through a resistance I I from a direct current supply S and discharging through a ball gap device 9, so as to initiate in the secondary l2 coupled to the primary ID, a train of high frequency high voltage oscillations which appear on the main electrodes of the relay E. The electric data of the timing generator are so adjusted as to give to these oscillations a maximum peak that is appreciably beyond the normal breakdown potential of this relay, so that normally it does not strike; and that each quenched oscillation impulse is separated from the following one by a time interval exceeding the deionisation period of the relay. The supply generator GA comprises a source of continuous current S charging the condenser I5 through a resistance IS. The time constant of this latter circuit is adjusted so as to be substantially inferior to the time interval between the recurrent H. F.

impulses furnished by the transformer Ill-l2. On the other hand, as the resistance of the circuit through which the condenser l5 discharges during the striking period of the spark relay E is relatively small, the time constant of this latter circuit is generally many times less than that of the charge circuit of this condenser. To increase the amplitude of the recurrent H. F. voltage impulses furnished by the timing generator, a small condenser 60 may be placed across the secondary l2 as indicated in order to form a circuit responsive to this H. F.

This system operates as follows: Assuming first that the continuous potential on the starting ring 6 is below its ignition value and is, for example, at 1;

zero voltage, high tension impulses will periodically appear between the main electrodes 4 and 5 and form between them an electric field which is not strong enough to initiate a breakdown of the air gap. The starting electrode exerts no appreciable action on this field but, if its potential reaches a determined striking value, then it will push the lines of forces toward the main electrodes and increase the field strength sufficiently so as to initiate the breakdown of the gap. As long as this starting potential will remain on the starter, each H, F. voltage impulse furnished by the timing generator will give rise in the discharge circuit to a current impulse through the intermittent spark conductors, and this current impulse will energize the load; in the example illustrated by lighting the signalling lamp I4.

It must be noted that the control device, in this case the battery it, has only to furnish a-very feeble current barely sufiicient to charge the minimum capacity (of few electrostatical units) between the ring 6 and the electrode 5 and therefore the input control energy necessary to fulfill the control efiect is practically negligible. As the starting ring acts only electrostatically and no discharge takes place between it and the other electrodes, and the spark breaks down only between the main electrodes, there are no losses in the control circuit, which enables this system to be operated from devices furnishing very feeble energy output, like photo-electric cells and so on.

A practical example will better illustrate the object and practical interest of this system. By giving to the main electrodes a distance of about 8 mm. and by utilizing a suitably located starting ring, I have secured current impulses of about one ampere, by giving to the recurring voltage pulses a value of about 10,000 volts. The relay operates by applying to the starting electrode a continuous potential of about 100 volts. Each voltage impulse was of a. H. F. oscillating form, its length was of about 10 microseconds (each impulse was formed by about 20 H. F. complete dampened oscillations) and the recurring interval was of of a second. The current impulses were also of an oscillating form and dampened by the choke coil I3, so as to stop the spark and avoid a permanent arc discharge between two timing voltage impulses. But, without this coil, the recurring frequency was sufficiently low as compared to the deionisaticn time to secure a periodical firing of the gap and, therefore, to transform the continuous input control voltage into a series of current impulses.

The supply generator GA permits the increase by many times of the current amplitudein the cases where it is necessary to fulfill it in order to operate a given device in the load circuit. As soon as the relay strikes, the condenser I5 discharges through it giving rise to a strong current of an exponential form. By giving to the discharge circuit of this condenser a time constant value (RC) of 10 seconds, and to the charging circuit a time constant of 10-*, I havesecured a very reliable operation. It must be noted that the train of a dampened H. F. voltage oscillation forms only a particular method of realization of my system and that the latter may be operated by applying any other form of voltage fulfilling only the basic condition to have a form of recurrent short high tension impulses separated by a time interval substantially greater than the deionisation period of the relay.

The described system is particularly well adapted for simultaneously operating a large number or air gap relays, of the same apparatus: as, for example, an automatic piano with electrically controlled keys; a distance controlled automatic machine fulfilling multiple operations; a large television screen formed by eiectro-optical elements separately controlled by the incoming video pulses, and the like.

In Figure 2, I have illustrated the application of the above system to control the operation of two piloted arc relays as described and claimed in my U. S. Patent No. 1,668,615. This relay, forming no subject of the present invention, will be mentioned briefly. Each relay comp-rises an electromagnetic coil Zt which field insures the rotating movement of a strong are between th outer and inner electrodes of the relays is! and 20. An alternator 21 feeds these relays through output resistances 5| and 5| and the protecting condensers 26, 28' and stabilizing coils 23 and 2-3;

which was explained in detail in the prior U. S. patent. The operation of these relays is controlled by the coils I3 and I3 as in the output coil [3 of Fig. 1. The current impulses sent through these coils by the system of my present invention produce therein voltage impulses starting the arc relays. This system will be shortly described again, and to make its understanding easier, I have used the same references to designate the same devices, but with primes and double primes. References 4, 5', 6 and 4", 5", ii indicate two spark gap relays controlled by the input circuits schematically designated as 34 and 39. The output circuit of each relay comprises, in series, the main electrodes, the coil 12 or 12 feed by a primary It and furnishing to the relay the train of H. F. high tension impulses; a small capacitor 41 or as, and a coil 42 or 5B. The latter are coupled to the secondary windings E2 or I 2" and are used to apply through the last men- H tioned capacitors, to the starting rings 6 or 6" a potential which compensates the voltag induced therein by the varying potential of the main electrode 4, 4", and protects therefore its control efiiciency against it. The secondary IE] of the timing generator is supplied by a quenched oscillation generator formed by a ball gap 9 and a condenser 8 fed by the alternator 21 through a transformer 52, time base resistance 5! and a choke 30. The use of the same alternator to feed the load device and the spark gap relays 'auto matically secures a perfect synchronization condition between them. Ihe condensers IE and i5 supply strong current through the spark cir cuit and are charged through resistances it and In Fig. 3, I have represented the application of my invention to an alarm system controlled by a photocell, the output of which is transformed, when it exceeds a certain critical value, into a series of current impulses which operate an alarm device. In this figure, the previously described elements of my impulse system performing the same functions are designated by the same reference characters and are only briefly mentioned. They comprise, enclosed in a dash-line rectangle, the spark gap relay its timing generator GT furnishing the H. F. high tension impulses, and the energy supply condenser of the supply apparatus GA enclosed in a dash-line rectangle S. I enclose in the rectangle T a common feeding device supplying both the generator GT and the apparatus GA. The rectangle L surrounds the operated alarm device and the rectangle C encloses an auxiliary amplification device interposed between the photo-cell l2 and the spark gap relay in order to secure the continuous voltage level necessary to energize this relay. This amplification device is of a free air ionisation type as described and claimed in my presently copending application Serial No. 766,034. It comprises a point-shaped electrode [3 acting like a cold cathode and producing ionisation of the air sheet surrounding it, a collecting electrode l6 acting like an anode and put to a high positive potential; two ring-like grounded electrodes '14 acting as electrostatic shields and between them a grid-like control electrode 55. The photo-cell, which may be particularly sensitive to infrared rays and detect therefore the beginning of a fire, or which may detect radio-active emanations, is connected between the grid 5'5 and the ring M. Its amplified output changes the continuous voltage on the output resistance 12 in the collector circuit of the amplifier. This voltage is applied to K I u the starting ring 6 of the spark relay in order to secure its breakdown when the voltage has exceeded a certain critical amount. The current pulses charge a condenser 34 in series with the main circuit of the spark relay, and this condenser discharges through the winding ll of an electro-magnet H energizing the alarm bell 18. An interrupter 30 permits the operator to cut the auto-blocking relay winding 89 and to stop the bell.

A single battery Tl supplies all energy to the entire apparatus. First it feeds a relaxator comprising a large condenser 19 and an electro-magnet winding l8 of a very sensitive relay. This latter acts as a periodical interrupter, closing the relay 89, for example, every ten seconds, for a short time interval. During this short closing period the heating filament of a rectifier is connected to the battery Ti and simultaneously, the relay 89 energizes the primary windin 8| of a transformer, the secondary of which is connected in series with the rectifierand a condenser 83. The opening of the primary winding circuit induces a high tension impulse on the secondary, which is rectified and charges the condenser iiB. The voltage on it is used, after the usual filtering, to feed the ionic amplifier i5 and also to charge the condenser l5 of the supply generator GA.

The timing generator GT is fed by means of a transformer 84, the primary of which is in series with the interrupter 89.

This apparatus oiiers the advantage of requiring only a small battery to supply all working voltages, and as the ionic amplifier and the spark relay need no heating current, and the rectifier valv is heated only by intermittence, the energy losses are very minute, and makes this apparatus particularly well adapted to all portable equipment. 1

What I claim is:

1. In an apparatus for generating recurrent short current impulses in an output circuit, an open air spark gap device comprising two main discharge electrodes spaced apart in open air and a starting electrode displaced from the discharge path between said main electrodes, an input circuit connected between the said starting electrode and one of said main electrodes, said output circuit connected in series with said main electrodes, an energizing generator in series with said output circuit and said main electrodes for producing recurrent high tension short impulses, the peaks of said impulses insufiicient in magnitude of themselves to initiate breakdown of air in said path, and means in said input circuit furnishing a time varying electrostatic potential having voltage values sufficient to enable initiation of a spark discharge only in said path between said main electrodes in response to said impulses.

2. Apparatus in accordance with claim 1, wherein said energizing generator furnishes a train of high tension recurrent impulses separated by time intervals greater than the deionization time of said spark gap device, each impulse being formed of several high frequency damped oscillations.

3. The combination in accordance with claim 1, wherein said energizing generator comprises a condenser, and means to charge said condenser, a ball gap discharge device connected so as to discharge said condenser periodically, and means to generate a train of recurrent hi h frequency damped impulses in response to each discharge,

7i and" a transformer the, primarywinding of which is in series with the said ball gap and the high tension secondary winding of which is in series with said output circuit.

4. In an apparatus for generating recurrent short current impulses, an open air spark gap relay device comprising two main discharge electrodes-spaced apart in open air to provide a discharge gap, and a starting electrode displaced from said discharge gap and adjacent said main electrodes, an input circuit connected between the said starting electrode and one of said main electrodes, an output circuit connected in series with said main electrodes, an energizing timing generator in series with said output circuit, said generator producing recurrenthightension short impulses the peaks of which are insufficient normally to initiate breakdown of said gap, a load device in said output circuit, means in said input circuit furnishing a time varying electrostatic potential for initiating a spark discharge in response to said impulses only in said gap between said main electrodes and only when said time varying potential exceeds a critical level, and meansin serieswith said output circuit to supply energy to said load during said spark discharge.

5. In an apparatus for generating recurrent short current impulses, an open air spark gap device comprising two spaced main discharge electrodes, a starting electrode displaced from said discharge gap between said main electrodes, an input circuit connected between said starting electrode and one of said main electrodes, an output circuit connected between said main electrodes, an energizing timing generator for applying voltage in series with said output circuit, said generator producing recurrent high tension short impulses the peaks of'which are insufficient normallyto initiate breakdown of said gap, a load device in series with said output circuit, means in said input circuit for furnishing a variable electrostatic potential adapted to enable initiation of a spark discharge only in the gap between the main electrodes and only when said potential exceeds a critical level, a condenser in series with said output circuit, a source of continuous current connected to charge said condenser through a resistance, the values of said condenser and resistance being chosen to providea time constant substantially less than the time interval between said recurrent high tension pulses.

6. Ina system for generating recurrent short current impulses, an open air spark gap device comprisingtwo main spaced discharge electrodes of spherical form, a starting electrode of, annularform, said starting electrode located between said main electrodes so that the discharge gap between said main electrodes passes through the opening'of the annulus, an input circuit connected between the said starting electrode and one of said main electrodes, an output circuit connected between said main electrodes, an energizlng generator for applying recurrent high tension short voltage implses in series with said output circuit, the peaks of said impulses insufiicient: in amplitude normally to initiate breakdown of said gap, and means in said input circuit providing a variable electrostatic potential adequate to initiate a spark discharge only in the gap between said main electrodes when said electrostatic potential exceeds a critical level.

7. In combination, a pair of main discharge electrodes separated in open air by a discharge.

path, a source of voltage and a load circuit in series with said discharge electrodes, an electrode adjacent to but displaced from said discharge path, means for applying a D. C. voltage of variable magnitude between said electrode and one of said main electrodes, a source of recurrent voltage pulses, means for applying said recurrent voltage pulses in series with said main electrodes, said voltages pulses having sumcient magnitude to initiate a discharge only in said discharge path and only when said D. C. voltage exceeds a critical value.

8. The combination in accordance with claim? wherein said electrode is an annulus surrounding said discharge path.

9. In combination, a pair of main dischargeelectrodes separated in open air by a discharge path, an auxiliary electrode adjacent to but displaced from said discharge path, a condenser, a load circuit, a further circuit inter-connecting said load circuit, said condenser and said main discharge electrodes in series, a source of recurrent oscillatory pulses, means for applying said recurrent oscillatory pulses in series with said further circuit, means for charging said condenser to a predetermined voltage, means for applying a variable electrostatic voltage between said auxiliary electrode and one of said main electrodes, said variable electrostatic voltage insufficient of itself to effect discharge to said auxiliary electrode, said predetermined voltage and the amplitude of said oscillatory pulses having magnitudes sufficient to initiate discharge only in said discharge path between said main discharge electrodes only for values of said variable electrostatic voltage exceeding a critical level.

10. The combination in accordance with claim 9 wherein said auxiliary electrode is an annulus surrounding said discharge path.

PIERRE MARIE GABRIEL TOULON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

